Known circuit breaker arrangements can be used for medium voltage applications ranged between 1 and 72 kV of a high current level. These circuit breakers can be used in electrical networks to interrupt short circuit currents as well as load currents under difficult load impedances. The vacuum insert of the medium voltage circuit breaker can interrupt the current by creating and extinguishing the arc in a closed vacuum container. Known vacuum circuit breakers can have a longer life expectancy than air circuit breakers. Moreover, current interruption with vacuum means is one technology that can be used at a high voltage level. Shielding means and grounding means can be used as safety measures.
The document WO 2009/043361 A1 discloses a pole part of a medium voltage circuit breaker. A vacuum insert containing a pair of corresponding electrical contacts is embedded in insulating fashion in an epoxy resin encapsulation. The upper electrical contact within the vacuum interrupter chamber is fixed while the lower electrical contact within the vacuum interrupter chamber is movable. The movable electrical contact is passed to the outside via bellows and can be moved by an axial movable jackshaft. In order to create the electrical transmission between the lower movable electrical contact and the corresponding lower terminal, a metallic electrically conductive connection is provided between a push rod of the movable electrical contact and the outer terminal. That metallic electrically conductive connection includes a piston, which runs movable within a metallic electrically conductive cylinder which is moulded in the insulating housing of the pole part and which forms said upper terminal of the pole part.
The insulating housing of the pole part is open at the bottom in a known manner. The pole part can be connected on a mounting surface of a gear housing at the bottom side by screwing. The gear housing is provided for accommodating the jackshaft arrangement for operating the push rod of one or more pole parts mounted thereon.
In circuit breaker arrangements, the distance between high voltage parts and grounded parts can be so short that additional means are specified to realize the highest insulation voltages that are requested by the industrial standards. Some standards additionally specify creepage distances that are longer than the distance between the high voltage parts and the grounded parts.